Signal system



Oct. 29, 1935.

c. E. BEACH SIGNAL SYSTEM Filed Nov. 5, 1931 3 She ets-Shee't 1 IN TfkFf/FE/VGE Oct. 29, 1935.

, c. E. BEACH SIGNAL SYSTEM Filed Nov. 5, 1931 3 Sheets-Sheet 2 Oct. 29, 1935. c. E. BEACH 2,018,656

S IGNAL SYSTEM Filed Nov. 5, 1931 5 Sheets-Sheet 5 Patented Oct. 29, 1935 UNITED STATES PATENT OFFICE 24 Claims. (01. 177-367) This invention relates to signaling systems and energy sources therefor, and is particularly suited for use where it is desirable that signaling systems shall accomplish results such as are ;.i generally contemplated by my prior Patent 1,528,596, for Signal system, dated March 3, 1925, but where such signaling systems have functional characteristics and/or are subjected to service conditions which none of the energy sources disclosed by said patent fully meet in a satisfactory and continuously efficient manner.

For example, certain of the arrangements disclosed by said patent contemplate utilization of what is generally termed a three-phase delta or star-connected energy supply, while other arrangements disclosed by said patent contemplate the use of a so-called single-phase" alternating current, without any direct current mechanism.v In the utilization of such arrangements, it is obvious that theelectromagnets of instruments connected in the signaling circuit should be of a type which adapts them for energization by alternating current and it istherefore apparent that arrangements for utilization of single or multiphase sources are unsuited for signaling circuits comprising instruments having electromagnet structure which does not operate satisfactorily with alternating current.

In many instances thisis an important consideration; for example, where existing systems comprise a comparatively large number of instruments, as signal initiating stations, equipped with magnets unsuitable for energization by alternating current, or where it is desired to utilize in 85 proposed new systems, without modification, types of instruments having successful service records extending over avlarge number of years, notwithstanding the fact that the types of instruments having such service records are, almost 40 without exception, only obtainable on a commercial basis with magnets suited only for unidirectfonal current energization. In this connection it should be noted that most of the signaling instruments of the generally used commercial 45 forms are of such design and arrangement that mod'iication of the electromagnet structure is likely to involve changes in form and shape which would necessitate extensive rearrangement of parts and alteration of general dimensions, 50 thereby precluding utilization of existing faciliiies for manufacture.

In addition to the foregoing considerations, there are situations where single-phase alternating current is available, but where multi-phase 55 alternating current can be obtained, with ordinary commercially available equipment, only with moving appliances such for example as rotary converters, and where the utilization of a constantly operating mechanism of such character is deemed objectionable, from various con- 5 siderations such for example as impracticability of providing constant supervision.

Furthermore the arrangements disclosed by said prior patent for supplying energy to a signaling circuit from a single-phase alternating 10 current source involve niceties of arrangements of relative inductance and resistance of alternative current paths which have been deemed objectionable in various instances as, for example, in the case of municipal fire-alarm systems in 16 which the signal initiating stations comprise socalled "non-interference electromagnets. Such magnets are normally shunted out of the series circuit but are brought into the circuit during activity of the mechanism, whereby the effect 20 of the phase-splitting inductances at the central office may be objectionably disturbed if not substantially neutralized by inductance changes in the outside line, which renders it extremely dimcult to maintain a desirable degree of equivalent 25 mean effectiveness, of the electromotive forces supplied between the ends of the metallic circuit and the ground.

In the aforesaid prior patent there are also disclosed arrangements for supplying the nor- 30 mally closed metallic path of asignaling circuit from a direct current source such as a battery, and for applying an alternating current potential between the metallic circuit and the ground, either through the connection of an alternating current source intermediate the battery terminals "or by alternately grounding the terminals of the battery which normally supplies the metallic circuit. With the first-named arrangement satisfactory results have been obtainable only through use in the metallic circuit of instruments responsive to either direct or alternating current, while in the instance of the second arrangement. deterioration of contacts for applying the ground connection to one side and the other of the normal current source and the maintenance of constantly operating mechanism of this character have been deemed objectionable. g

It is the general object of this invention solve the problems just outlined and other prob lems inherent in previously proposed arrange ments. More specifically it is one of the main objects of this invention to provide current supply equipment for signaling systems whereby energy from a two conductor alternating current 56 50 illustrating the operation of the new system unsource is so applied to a three conductor utilization system that the potential between any one and another of the utilization conductors is unidirectional. It is a further important object to provide such current supply equipment in which the mean value of the unidirectional potential applied between any one and another of the three utilization conductors is adequate for intended signaling purposes. Still another object of this invention is to provide current supply equipment whereby energy from a two conductor alternating current source maintains a unidirectional current through a normally closed current path and also maintains a potential between such current path and an associated conductor (such for example as the ground or the sheath of an underground cable), whereby leakage between such circuit and conductor/may be instantly manifested without thereby impairing the eifectiveness of the normally closed circuit for signaling purposes.

In another aspect the present invention has the further object, in order to meet certain service conditions, to provide unidirectional current for energizing certain of the utilization conductors while at least one of the conductors is energized by alternating current, whereas in other situations, where it is altogether undesirable, alternating current may be excluded from the controlling magnets of the instruments in all of the current paths, unidirectional current being substituted therefor.

In a still further aspect the invention provides means for employing a plurality of rectifier-units .witha two conductor alternating current source so that, for each of a plurality of utilization conductors, "at least one rectifier unit is interposed between the conductor and the source of alternating current.

Other objects and features of the present invention will be apparent from the following detailed description illustrating the genus of the invention by explaining several concrete embodiments thereof which are illustrated in the accompanying drawings in which:

Fig. l is a circuit diagram illustrating the principal aspect of the invention;

Fig. 2 is a similar diagram illustrating a modification using only unidirectional instruments;

Figs. 3 to 5 are diagrammatic representations der different conditions;

Fig. 6 shows curves which approximately illustrate the configuration of the current flowing in different paths of a stem according to the invention, during various conditions thereof; and

Figs; 7 to 11 are circuit diagrams similar to Fig. 1, but somewhat simplified, showing various modifications of the invention.

Referring to Fig. 1, A, B and C are representavtlves of a number of signal initiating means,

tiated by code wheel 48.

sents the simplest type of signal station suitable for operation with acircuit according to the invention, and is described in my aforementioned Patent No. 1,528,596, comprises contacts 5|, 52 and 53 actuated by a code wheel 58 in such a 5 manner that under normal or inoperative condition of the box, contacts 5| and 52 are closed, thereby completing the series circuit of signaling means and receiving appliances, whereas, upon operating the box (usually. referred to as pull- 10 ing a box), all three contacts 5|, 52, 53 are first connected when 5| is lifted by a cam of wheel 58, and then disconnected when 5| is descending after having passed over the cam. The opening of all three contacts interrupts the closed circuit 15 for normal signaling, whereas the interconnection of all three contacts grounds the circuit for emergency signaling, each signal impulse comprising a grounding and an interruption.

The diagram of signal initiating station B rep- 20 resents the current paths provided in signaling stations functionally similar to the type of station disclosed by my prior patent for Successive non-interference signal box, dated January 2, 1917, No. 1,210,398 and comprises a non-inter- 25 ferenceelectromagnet 42, shunting contacts 4|, code wheel operable contacts 41 for signaling over the normal metallic circuit, contacts 43, 46 and 50 cooperating with segments 44 and 45, and

contacts 49 for establishing ground connection. 30

Upon pulling box B contacts 4|, which normally close the series circuit around the devices of the box, areopened, thus bringing the. non-interferencemagnet 42 and the signaling contacts 41 (normally closed) into operative relationship 35 with the circuit. Magnet 42 is thereupon energized and, assuming that the system is in normal condition, permits signaling over the usual or normal metallic current path, which is ini- The wheel opens and 40 closes contacts 41, thereby opening and again closing the signaling circuit according to the code signal assignedto this box, and upon completion of the sending cycle, the box is restored to normal condition. It iswell understood in 5 the art, and fully described in my aforementioned United States Patent No. 1,210,398, that non-interference magnet 42 reiiders its box ineffective to interfere with the signals sent by the other boxes of the circuit if B should be pulled 5 when any of these boxes are sending. During operation when the circuit is in abnormal condition each signal impulse establishes connection of one or the other side of the line to ground, as described in theabove identified patent. 55

The station C is representative of stations having functional characteristics similar to those of the mechanism shown and described in the patent to F. W. Cole, No. 553,838, for Successive non-interference signal box, dated February 0 4, 1896, comprising normally closed contacts 3| for shunting the electro-magnet windings while the box is at rest, contacts 35 and 36 for normal signaling over the metallic circuit, and non-interference magnet windings 33 and con- 5 trolling contacts 39, windings 33 being connected across contacts 3|. The outside terminals of 33 are connected to contacts 35 and 36 respectively which are arranged for interconnection therebetween and with the wheel contact 31 in- 70 cident to the engagement therewith of the teeth of the code wheel 38. The normally open contact 39 is operable bythe box mechanism to effect closure of the normally open ground c0nnection. Contacts 35 and 36 are for normal sig- 75 naling when contacts 39 are open. However, when the latter are closed during emergency operation, each connection between 35 and 36 is of this type.

The receiving station, connected with the outer circuit at 26 and 21, comprises four asymmetric conductors I, 2, 3 and 4 of suitable type, hereinafter referred to as rectifier-s, which are connected in a bridge circuit with terminals I I I, H2, H3, Ill intermediate the rectifiers which conduct current substantially only in the direction of the arrows of their symbols. The opposite terminals III, II2 are connected over the secondary winding 1 of a transformer T having a. primary winding 6 which is supplied over terminals 9 and I0 from a suitable source of single-phase alternating current, as. for ex ample a single phase alternating current generator 1'. purposes of this invention, the secondary 1 constitutes the real source of current, the references herein to an alternating current source being intended to signify any instrumentalities employed for applying an alternating electromotive force between the portions of the circuit to which the ends of winding 1 are shown to .be connected.

A resistance 8 may be inserted in series between winding 1 and terminal III. Terminal III is also connected to one terminal of a manifesting device G of conventional design, whose other terminal is grounded, this arrangement providing a common return conductor from any grounded point of the outer circuit to the receiving station. The two other opposite terminals I I4, II 3 of the rectifier bridge are connected to two manifesting devices E and F and these to the receiving station terminals 26 and 21 which are joined to the incoming ends of the outer circuit, so that H3 and II 4 join the power supply with a normally closed signal circuit loop including signal initiating and manifesting devices.

In the embodiment shown in Fig. 1, the manifesting device G must be of the universal" type, that is responsive to both alternating and unidirectional current, whereas E and F as well as the magnets of the signaling boxes need only be operative with unidirectional current, whereby the term unidirectional, as employed throughout this specification as defining direction of potential or current fiow applied to or in a given current path, is used to distinguish from alternating current, potential or current fiow, in the sense of the significant or practical effect of such potential or current fiow, as distinguished from what might be considered, under some circumstances, asv the apparent potential or the theoretical potential or current flow developed or occurring, for example, /incidental to certain uses of asymmetrically conducting units.

It is sometimes feasible and desirable to employ exclusively apparatus responsive to unidirectional current not only in the outer circuit but also in the manifesting circuit, and

It is, however, understood that, for

vices e and f with magnets GI and 62 and armatures 65 and 66 normally attracted by the magnets continuously energized-by the closed signal circuit. Magnet 63and armature 61 are of similar unidirectional design but normally deenergized and released respectively. Magnet 63 is part of another rectifier bridge comprising rectifiers II, I2, I3 and It, being connected across the opposite terminals 13 and 14 of that bridge. The two other opposite terminals H and 12 of the bridge are connected to ground and to terminal III of the current supply bridge respectively; such bridge and magnet arrangement constituting the third manifesting device 9. Aside from the different arrangement of the grounded manifesting device Figs. 1 and 2 are in general principle identical and it is evident that the current fiow in magnet 63 is always unidirectional no matter what its direction may be in the ground conductor. This feature is also brought out by the arrows indicating the current fiow of Fig. 5.

The conventional register shown in Fig. 2 by way of example comprises pens I1I, I12 and I13 attached to resilient arms 15, 16 and 11 which are normally lifted from the recording tape t whereas, if armatures 65 and. 66 are released, pens HI and I12 contact with the tape upon swinging over stops 8| and 82 and bending back again from the tape. Similarly, pen I13 in cooperation with stop 83 marks the tape upon armature 61 being attracted and then released by magnet 63. It will of course be understood that this particular manifesting device is merely described as a comparatively simple example of such apparatus and that any other suitable arrangement may be employed.

The operation of the new system under normal and various faulty line conditions will now be described with particular reference to Figs. 3 to 6, Figs. 3, 4, and 5 being simplified diagrams, with current paths, of an installation according to Fig. 2.

Under normal non-signaling conditions, when the series circuit of the line is closed within each alarm box and not grounded and when the line is sound (Fig. 3), if the transformer secondaryy 1 is energized, in the direction of arrow I3I, by one half cycle of an alternating current having a general configuration according. to curve IUI of Fig. 6, the valves of the rectifier bridge permit current-flow only as indicated by full line arrows;

from terminal III, over rectifier 3, terminal II3,

manifesting device I, line, manifesting device e, terminal 4, rectifier 4, terminal H2, and thence back to 1. During the next half cycle, when current flow is in the direction of the dotted arrow I32, the current is conducted from terminal H2 over rectifier 2, terminal II3, manifesting decurrent such as is represented by curve IIII.

Since the signaling current path, for example from terminal II3 (Fig. 3) through lA-B-- C-e to I it includes both inductance and resisting electromotive force I02, but is in addition inance, the shape of the current pulsating in this circuit corresponds not strictly to that of pulsat-- fluenced by induced electromotive forces, counteracting, or supporting electromotive force I02 during the latters increase and decrease, respectively.

During the valleys of curve I02 (representing the rectified exciting electromotive force), the supporting electromotive force due to the inductive resistance of the electromagnets of the signalling circuit induces a current, herein referred to as circulating current, which has two paths, namely (referring for example to Fig. 3) from the line through e-I I 4-I-I I I--3--I I 3f back to the line, and from the line through e- I I4--4--I I2-2-I I3-f back to the line. In this manner a circulating path comprising two concurrently effective parallel conductors is provided, each parallel conductor excluding the alternating current source, and including two rectifier units in series, all rectifiers being conductive in the same direction within the circulating path. It is evident that the presence of this direct circulating path, which is free from the impedance of the transformer secondary, enhances the effectiveness of the induced current for smoothing the rectified current due to the impressed unidirectional electromotive force. The approximate shape of the smoothed current is indicated at I02 of Fig. 6. If an alarm box, for example B, is pulled, it interrupts the closed signal circuit and operates manifesting devices e and f as above described. With this type of box, as well as with a type corresponding to box C, the ground is disconnected during normal operation and device g therefore not affected, whereas box A grounds the system with every signal impulse, with a resulting current flow operating also manifesting device G, in a manner which will be easily understood from the following discussion of operation under faulty circuit conditions.

Should the signal circuit be broken at a point a as indicated in Figs. 1 and 4, the electromagnets of manifesting devices e and 1 would be deenergized, and such devices would thereupon act to indicate that the circuit had been broken. While the normal current path was thus interrupted, activity of any boxes such as A, B and C would cause the formulation of a series of signaling impulses eifective through that portion of the circuit which remains unimpaired between the active box and the central oflice, and thence through the ground. In thecase of box A, such signaling current path would become effective due to the fact that this box establishes a ground connection incidental to'each signaling impulse. In the instance of box B, because, due to the broken line condition, no current would be flowing in the normal path, the non-interference magnet 42 would fail to become energized when the shunting contacts 4| are opened, so that the succeeding operation of the mechanism would in due time effect closure of the ground current path and thereby enable the mechanism to send the intended signal through the ground and whichever side of the circuit remained unimpaired, utilizing contacts 43 to 46, 49 and 50 as described at length in Patent #1210398. In the instance of box C, there would be corresponding action due to actuation of contacts 39 as more fully described in Patent #553,838.

As mentioned before, when the conditions of the system are normal, that is when the usual metallic current path is closed, and no signal is in course of formulation, a current path is established from one terminal of the secondary winding I of the transformer through rectifier 2 or rectifier 3 (depending upon the direction of current flow in winding 1) to terminal I I3, thence through manifesting device I, through boxes A, B and C, manifesting device 6, terminal H4 and rectifier I or 4 (again depending upon the direction of current flow through secondary winding 1) and the other terminal of winding 1.

So long as the current path just traced is maintained, the electromagnets of the manifesting devices e and f are effectively energized; but upon interruption of this current path as by a circuit break at a, the electromagnet windings of the manifesting devices e and f become deenergized and remain so, either until the normal current path is restored or until an emergency current path is established through the ground connections. However, if such an emergency path is established from the portion of the circuit extending from break a to manifesting device 1, the electromagnet windings of device f, are effectively energized, but the electromagnet windings of the manifesting device 6 are not energized. correspondingly, if the portion of the circuit between break a and manifesting device 6 is connected, the electromagnet of device e is effectively energized but that of manifesting device I re-.

-mains deenergized. If, while the circuit remains broken at a, ground connections are applied to the portions of the circuit at both sides of the break, the electromagnets of both manifesting devices e and f are effectively energized. Theoretically, the characteristics of the current flow incidental to closure through the ground of a broken line at one side or the other of the break, might be represented by the curve I03 of Fig, 6 (in the absence of inductance in the current path) since only one series of alternating half cycles of the alternating current is operative in this circuit, the other series being ineffective since the line is open at a. This theoretical current is diagrammatically indicated by the rectangular dashes of. Fig. 4, and flows from secondary I through I I 2--2--I I3f-operative line portion- A-B-ground g-I I I back to I. Similarly as explained when describing normal signalling conditions with reference to Fig. 3, the inductance of the signalling circuit induces electromotive forces which have the same direction as isolated half waves I03 during the intervals between these half waves. The corresponding induced currents flow in an unobstructed circulating path analogous to that traced for Fig. 3, but in this case including a grounded point and the emergency conductor. The path and the approximate configuration of this induced current are indicated by the pointed dashes of Fig. 4 and it follows that the manifesting devices g and f, as well as the noninterference magnets of the alarm boxes, are in this manner supplied with a reasonably smooth unidirectional current flowing in the same direction as during normal operation and approximately indicated by curve I05 of Fig. 6.

Describing now the actual signaling, and referring again more particularly to box B by way of example, the continuously deenergized noninterference magnet 42, establishes a circuit closed over ground by first connecting contact 46 with 43 whereupon 42 is energized over normally closed contacts 47, and starts rotation of code Wheel 48 which opens and closes contacts 41 as under normal operating conditions, with the difference that the circuit is now closed over 48, 44, 43 and 49 to ground instead of relying upon the normal path over wire 2| to the adjacent box. At-the conclusion of the sending operation,

contacts 49 are opened and 43 is in neutral position. It is of course irrelevant at which place of the line the break occurs. For example, if the break should occur at b at the other side of box B, the operation is quite analogous, with the only difference that the alternate set of half ways of impressed electromotive force (curve I04 of Fig. 6) is now effective. The magnetically induced circulating current flows during the inefiective half cycles of the alternating current source through a circulating path including rectifier I,

and smooths out the half cycle series indicated at I04. In this case manifesting devices e and g respond.

It is well known that ground connections have in most cases a higher resistance than the normal metallic signaling circuit, and it will now be evident that the present system has the following advantage related to this fact. In order to provide under both normal and abnormal conditions signaling currents of approximately similar magnitudes, it is desirable to apply a higher electromotive force when signaling through ground than for operating with the normal circuit. In the present instance (referring for example to Fig. 1) the normal circuit is supplied through rectifiers I and 2, or 3 and 4 in series,

during respective half cycles, which devices cause a certain fall of potential. On the other hand, whenthe ground connection is closed, the output of the secondary winding 1 need pass through but one rectifier unit at any given time. Thus, for example, when the direction of current flow in secondary I is toward terminal III, the path then effective extends from said terminal through the ground to terminal H4, and thence through rectifier unit 4 to terminal I I2 of secondary I. During the next half cycle, the current path passes from this secciidary coil through terminal H2, rectifier unit 2, terminal H3, the right-hand portion of the circuit shown, and back through the ground to terminal III, which contacts with the opposite end of the winding I without passing through a second rectifier unit.

From the foregoing it is apparent that the noninterference and succession effects of alarm boxes, for example of the type of box B, are effective under the described emergency operation. For example,with a break at a, box B being pulled, and subsequently also an adjacent box of similar design between box B and terminal 2'I the non-interference magnet of the adjacent box would be caused by the signaling of Bnot to permit signalingby its box over the emergency path presentedby B. However, as soon as B com pletes its signaling, the other or seeking box encounters the same faulty condition as B originally did, and proceeds to send emergency signals similar to B.

Assuming that, with the line broken at a, box B is first pulled and then box C, these boxes would in due time act to .apply their respective ground connections, and such action of box B would tend to prevent effective energization of the non-interference magnet 33 of box C. When, however, box B completed the formulation of its intended signal and thereupon opened its ground connection, the non-interference magnet 33 of box would be energized, and thereby effect release of the signaling contacts 35, so that the subsequent actuation of these contacts by the wheel 38 would cause intended response ofthe manifesting devices I and 9'.

The operation of alarm boxes of the type A and C will be easily understood in view of the foregoing, and the prior descriptions of these devices.

Another possible faulty condition is in the nature of leakage to ground, for example if the line 5 is grounded at c as indicated in Figs. 1 and 5. Tracing the current flow in the system under such conditions, from the terminals III and H2 of the transformer secondary I, when the alternating current in I flows during a certain series 10 of alternate half cycle periods from III towards H2, its path continues from H2 over rectifier 2, manifesting device I and the right side or branch of the line to 0, branches there on the one s de from 0 over ground and manifesting device g to terminal III, and on the other side from 0 over the left side or branch of the line, manifesting device e and rectifier I also to III. The current flow during this half cycle series is indicated in Fig. 5 with full arrows. During the alternate half cycle series, when the current in I flows from I I2 towards II I, it continues on the one side from IH- over rectifier 3, terminal H3, f and the right branch of the line to c, and on the other side from III over g and ground also to c. From 0, there is a common path for this half cycle series from 0 over the left branch of the line, e and 4 to H2. This half cycle series is indicated in Fig. 5 with dotted arrows.

Due to the branching of the current paths, the line branches carry unequal amounts of current, since part of the-flow is always diverted over ground. For example, during the half cycle series whose current fiow is indicated by full arrows, the left-hand line branch (in parallel with the ground connection) carries less current than the righthand line branch. The magnitude of this current is diagrammatically indicated at m of curve I06 of Fig. 6, curve I06 symbolizing the current flow in the left-hand branch. The larger current simultaneously flowing in the right-hand branch is indicated at n of curve I01 which symbolizes the current flow in the right-hand branch. Similarly, during the alternate series of half cycles, the left-hand branch carries more current 15 than the right-hand branch, as indicated by 0 and p of curves I06 and I01. These currents are again smoothed out (as approximately indicated in curves I06 and I01), due to currents induced by the inductances in the respective circuits and flowing through circulating paths unobstructed by the impedance of the alternating current source. The ground connection, through which the current can flow in both directions, carries a current composed of components having the approximate configuration of curves I06 and I 01, one of these curves however being reversed, the resultant having the approximate configuration of curve IOI. Therefore, if the line is grounded, and although none of the alarm boxes is operated, 0 the current in the ground connection energizes manifesting device g, which is normally deenergized if the system is sound, thereby indicating a trouble condition, and also its nature. Manifesting devices e and remain energized, as under 5 nOrmaL'ungrounded line conditions. Also, in a system according to Fig. 1, the instrument g must be capable of being responsive to alternating current and unidirectional current whereas, if the circuits are organized according to Fig. 2 with 7 a second rectifier loop for the manifesting magnet '63, this magnet only needs to respond to unidirectional current, so that, in this case, only unidirectional instruments, or magnets, are required.

The above described condition of the normally closed signaling system continues so long as the latter is grounded at am! point thereof, and, in addition to indicating the fault as hereinbefore discussed, it permits signaling in the following manner. Assuming that the'ground is established at c as indicated in Figs. 1 and 5, between box 0 and terminal 26, any signals originating in boxes A, B and C are manifested only by device 1 since 6 and 9 remain continuously energized by the unidirectional half wave series which flows over ground condition and left-hand line branch and can not be interrupted by signal impulses of any of these boxes. Similarly, if the ground occurs at a point between box A and terminal 24, manifesting devices f and a are continuously energized, whereas signals are received by e. Further, if the systemis grounded at any point intermediate the alarm boxes, any box can successfully send signals, which will be manifested at either e or 1, depending upon the location of the signaling box with respect to the ground, the manifestation being always in the line branch of the signaling box.

Concerning the operativeness of non-interference devices in case of a ground anywhere at the line, it is evident from the preceding description,

that, in spite of the ground, current is always present in all parts of the circuit so that these devices are operative within their respective sections of the line regardless of the ground. For example, if the line is grounded at d between A and B, alarm box A manifests its signals at f, and boxes B and C manifest their signals at e, with proper separation of their respective codes if they should be simultaneously pulled. Still further, the signalsare kept apart even if all three boxes are pulled simultaneously, box A manifesting at f and boxes B and C manifesting at e in orderly sequence, due to the action of their non-interference devices. Also, the ground connection does not substantially affect the strength of the current in the line. For example, conductors d-ground-I I I and d-line- II4 are in parallel, and both in series with d line--I I3, during one of the two series of alternate unidirectional half cycles. III being approximately the electrical midpoint of the current supply system, and d-ground--I II (being substantially without resistance), while augmenting the normal current in d-line-I I3, does not substantially afiect the current strength in d-line--I I4, so that all three manifesting devices, e, f, g are sufiiciently energized. Similarly, conductors dground-I I I and dline-I I3 are in parallel, and together in series with dline-- I I4, during the other series of half waves. Consequently, ii, with a ground at d, box A is pulled, manifesting device ,f records the current interruption according to the code, which e and g remain energized; and if boxesB and/or C are pulled, e records, with g and f stationary. The

hereinbefore mentioned feature that, if the line is grounded at (1, box A can initiate signals at f and subsequently, or at the same time, boxes B and/or C can manifest at e, is explained from another point of view by the above described fact that; alternate sides of the line circuit are in series, and parallel with the ground connection,

- during alternate half cycles, so that each m1:

ing device g is deenergized every time when A and B interrupt the line simultaneously, since during such simultaneous interruption, both alternate series of half cycles are inoperative and the whole system, ground conductor included, is 6 without current. However, manifestations of this nature at. 9 will be easily interpreted as incidental, or rather indicative of simultaneous operation of boxes at both sides of a ground, since both devices e and f manifest at the same time clearly intelligible signals coming from these boxes.

Recapitulating, it may be said that a ground divides a circuit according to this invention into two separate, and for practical purposes indel6 pendent signaling circuits, the signal initiating and manifesting means in each circuit performing independently of those of the other circuit, including the well known features of successive non-interference" operation, but all operated by 20 unidirectional current of the same nature.

Another possible faulty condition is a short circuit, for example connecting points a and b of Fig. 1. Such a short circuit substantially deprives all alarm boxes of line current, and, so 25 long as none of these boxes are operated, E and F are energized, and G deenergized. Upon pulling one of them, for example box C, the following circuits are established during each ground ing impulse of the box. Considering first one of 30 the alternate series of unidirectional half cycles, the current of one such series flows from I through II2-2-II3--F-2'I- -24--b to a. At a, the circuit branches, one branch going from a through 2326E--I I4--I to III, and the 35 other branch from a through C-ground-G also to III, the circuit being closed from III through 8 to I. The other series of unidirectional half waves flows from I, in opposite direction, to III where the circuit branches. One branch goes (0 from I II through 3-I I3F-2l-24-b to a and the other branch from I I I through G--ground-C to a. From a, the circuit continues through 23- 26F--I I4--4I I2 to 1. Thus, manifesting devices E and F remain energized, but device G 45 responds to the signals from C at each interruption of the ground-line connection at C. Upon pulling box C, its magnetis not energized since no line current is present in C, so that it is permitted immediately to establish ground con- 50 nection for emergency signaling by closing contacts 39, whereupon the code wheel starts. to initiate the impulses. Upon completion of its signaling operation, box C again restores its mechanism to normal. 55

- From the foregoing it is also evident that the circuit is similarly operative in case of short circuits bridging less than all boxes, between a and b as assumed above, but bridging any box singly or any number of boxes collectively, in 60 any position within the circuit.

Under certain operating conditions it has been found that a resistance, such as 8, favorably in-v fluences the cooperation of the rectifier with the various conditions which may develop in the sig- 65 naling circuit and it was also found that changes in the relative positions of resistance and ground conductor may be desirable, depending upon the peculiar characteristics inherent in each particular installation. For example, the ground cir- 70 cuit may be connected directly to the rectifier bridge as shown in Fig. 1, or it may be connected between transformer secondary and resistance, as shown in Fig. 7. The difference of these two arrangements is not one of principle, but merely changes circuit characteristics under emergency operation, one or the other characteristic being preferable for individual installations. The difference of emergency circuit characteristics depending upon the use of installations either of Fig. 1 or Fig. 7 is the following one. It has been discussed at length especially with reference to Fig. 5, that the emergency manifesting device G can be either, during one alternate half cycle series, in parallel with the right-hand line and together with the latter, in series with the lefthand line, (dotted arrows of Fig. 5) or, during the other series of half cycles, in parallel with the left-hand line, and together with the latter, in series with the right-hand line (full arrows of Fig. 5). Considering now resistance 8 in relation with these emergency circuits, it appears that in a connection according to Fig. 1, the resistance is always included in series with the manifesting device G and one side of the line but never in shunt with G, which is sometimes called a long-series short-shunt connection. On the other hand, in an installation according to Fig. 7,

the resistance is in short-series long-shunt" conone or the other arrangement may be preferable in order to assure favorable emergency current distribution in a particular installation.-

In certain installations it may be desirable to omit one of the. manifesting devices for normal operation, for example F of Fig. 1, and to substitube for the ground manifesting device G a ground detector instrument D. Such an arrangement is shown in Fig. 8, somewhat simplified. In an installation of this type, ground trouble is detected by D, while signal manifestation takes place only through instrument E. Normal operation is as explained in connection with Fig. 3, the only difference being that signals are rec'eived at E only. If a break should occur at at, only the boxes between E anda remain operative, with a half wave series in the circuit from terminal 2 through |HD-ground-signaling boxE-l I4 to 2. As shown in Fig. 4, only the ,manifesting device which is at the same side nals from any point of the loop are received at both manifesting devices e and f, it will be evident that any signal despatched under these conditions in a circuit according to Fig. 8 actuates 1rglay E, the ground being indicated by detector Signals from short-oircuited boxes can not be received since, as will now be evident from the above description of signaling under such conditions with reference to Fig. 1, signals from shortcircuited boxes can only actuate manifesting devices in the emergency conductor. Sometimes) it may be desirable to make D sufliciently sensitiveto indicate currents of low strength. In this case, unless a second valve arrangement according to Fig. 2 is provided, instrument D should have high resistance and be operative for both Device series.

magnitude than that suflicient to operate D. In every other respect, an arrangement according to Fig. 8 functions in the same manner as an installation according to Figs. 1 or 2.

The embodiment illustrated'in Fig. 9 may have advantages under certain conditions. It comprises ,The terminals l2! and I22 of the transformer secondary are connected over asymmetric conductors 92 and 93, terminal I23, manifesting device F, line with alarm boxes A, B, C and manifesting device E back to tap 94 of the transformer secondary. One terminal of the transformer secondary is also, directly connected to ground. Under normal conditions, a circuit of this nature supplies the line with full wave unidirectional current substantially according to curve I02 of Fig. 6,;whereby signals sent by the alarm boxes are manifested through E and F. The current of one half wave series flows from 94 through secondary 91, terminal |2l--93-ll3 FA-BCE-9l back to 94, and the current of the other half wave series flows in circuit 94--98 I 22 -92--l 23F-A-BC- E9 l94.

If a break occurs in the line, for example at a,

the relay at the same side of the break as the sending box responds, actuated by one half wave For example, if box B is pulled, current flows from ground through l2l91-'a8l22- 92-l23-FAB back to ground, signals being received at F. If box 0 should be pulled, current flows in the other direction from 94 through 91 I 2 l-groundCE-9 l94, signals being received at E. During a trouble ground or emergency signaling ground an alternating current composed of alternate half wave series in the line branches flows through ground to terminal l2l. Assuming the ground to be at d,-one half wave series flow from 94 to l2! and branches there into l2lground d, and I2l93l23-F A-d, continuing through d-BCE9l to 94. The other half wave flows in circuit l2l-9'| 94-98-l2292--I23F--Ad; first branch dground-l2I9l--94, second branch d-B C-E9l94. The non-interference means of the alarm boxes will also operate substantially in the same manner. However, the' absence of a manifesting device in the ground conductor relegates all manifestations of changes in the circuit to devices E and F'which respond similarly to the corresponding elements of Fig. 1. In contradistinction from the heretofore discussed arrangements, the currents flowing in the line branches separated by a ground 0 may be of different strength. For example, assuming that, during a certain half cycle series (when the left-hand branch is parallel with the ground conductor and,

together with the latter, in series with the right-' hand branch), the current flows from -l2| towards I 22, and that the line is somewhere grounded, the whole transformer secondary l is effective in the circuit comprising HI, 1, I22, 92, I23, F, line, and groundc back to Hi. On the other hand, the alternate half wave series will be practically absent from the same branch, which' is during this period substantially in shunt with ground. Analogous conditions prevail upon the left-hand branch of the grounded circuit, where the alternate half cycle (corresponding to the period when ground and right-hand branch are in parallel, and together in series, with the lefthand branch), is in addition suppressed by valve 9|. However, irrespective of this alternate shunt-' ing of the branches over ground, the devices E and F remain operative with: their respective series of half cycles. x v

If any box or boxes are short circuited no signals originating therein can be received since. as explained before, under these conditions signals can only be received in the emergency conductor.

Still another embodiment of the invention is shown in Fig. 10, which differs from the arrangement according to Fig. 9 chiefly by omitting the rectifier in the lead to the midpoint of the transformer secondary and the manifesting device in the same branch, and by employing a ground detector D in the ground connection. Again, the circuit is normally energized with full wave rectified current flowing in the circuits traced above when describing the normal operation of the circuit according to Fig. 9, and signals can be normally received by device F.

If the line is broken, signals can only be received in a circuit including device F, and only if the signaling box is between the break and F, exactly as described in connection with Fig. 9.

At the presence of a ground, or when emergency signaling over ground takes place, this circuit performs similarly to that of Fig. 9. During the half cycle when the current in 1 flows from IN toward I22, the connection over ground from c to I2I is in series with 9'I98--|2292l23- F-line, and in parallel with the left-hand line branch leading from the ground to 94, the entire transformer secondary I being active, and the current in the right-hand branch being augmented due to the resistance of instrument D. During the alternate series of cycles, when the current flows from 91 towards I2I, the ground connection is in parallel with 949||2l93|23-Fline and both are in series with the left-hand branch, but the current will. be weaker since only the half winding 91 is active. Consequently, instrument D is energized by alternating current whose opposite half cycles are of unequal amplitude. Furthermore, the left-hand branch carries alternating current, since the loop circuit I2|9'|- 94linegroundl2l contains no asymmetric element. In the case of a short circuit, signals from short-circuited boxes can not be received, as explained in connection with Fig. 9.

The arrangement according to Fig. 11 differs from that of Fig. 7 mainly in the omission of rectifier I, so that the circuit under normalconditions carries only one series of alternate half cycles due to the electromotive force in the direction from-H2 to I ll, these half wave series flowing from I I2 through ll l-l |3Fline-E-- H4 back to H2. It will now be evident that in case of a break, signals are received at E and G from boxes between E and the break, and at F and G from a box between F and the break.

For example, if a break exists at a, and box C ispulled, signaling through ground, current of one half wave series flows from 2 through 1G-- ground-C--E-l l4 back to H2. If box B, on the other side of a is pulled, current of the other half wave series flows from 1 through ll 2-l I3-F- A-B- groundG back to 1.

If the line is grounded at any point,'for example d, the following right and left branched paths exist: One half wave series flows from I through ll2-l I3FAd-G back to 1. The other half wave series'flows from H2 through I and fromgthere in two branches, G-groundd and 8-I I |-l I3FA-d, where both branches unite and continue, through B-CE--l H to H2 and back to 1. Due to the presence of resistance 8, it can be assumed that said right and left paths, respectively, carry alternate half cycle series and the ground conductor alternating current. Therefore, manifesting devices E, F and G operate similarly as explained in connection with Fig. '7. In the case of short-circuited boxes, any such box is able to despatch signals through ground, to be received at device G, right-hand and left-hand branches, respectively, carry alternate series of half cycles, as will ,be apparent from Fig. 11. Manifesting devices, E, F and G operate similar to those in the arrangement according to Fig. 7.

Configuration of the signaling currents, as employed in this invention, is of minor importance,

provided they are unidirectional at every point where instruments which respond to such current only are employed. The shape of the current impulses is of minor importance because the mag nitude of the current frequency is very much higher than that of the transmission rate of the signals which are ordinarily sent over systems of this type, and also, as pointed out hereinbefore, because the inductance of the system smooths the unidirectional current waves, not

only those of the fully rectified current, but also the series of alternate cycles.

It is apparent from the foregoing description that the present invention permits successful emergency operation not only under the faulty conditions which have been expressly discussed, but also under other more or less similar troubles or combinations thereof. For instance, emergency signaling is possible irrespective of the fact whether a fault occurs upon the line between the alarm boxes, or within the boxes, or upon the lines leading from the boxes to the central station. Also, signaling is possible if for example, two gaps, two grounds, a gap and a ground, or a gap and a short circuit, etc., exist, with the exception of a few so-called electrically hopeless cases, where boxes are situated between two circuit faults such as grounds and/or breaks.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. Means comprising terminals for operatively associating a source of alternating current with a three-conductor utilization system, comprising four asymmetricvalves connected as a full wave rectifier bridge for excitation from a source of single phase alternating current, the terminals of said source being connected between respective pairs of valves, and two of the utilization conductors being connected between intermediate pairs of valves applying unidirectional energy representative of both of the half waves of the applied-alternating current between said two utilization conductors, a connection from the third utilization conductor/directly to one of the alternating current source terminals, and means for connecting and disconnecting any combination of two or three of said conductors, whereby a series of half cycles of said supply may be applied between said third conductor and one of the first named two utilization conductors, and the alternate series of half waves between said third conductor and the other of said two conductors, and whereby unidirectional paths may be established exclusive of the alternating current supply, said paths being constantly available from each utilization conductor to one and the other of the two remaining utilization conductors.

. 2. A two-conductor alternating current source and a three-conductor utilization system, in combination with connections involving asymmetric valve equipment interposed between said source and said conductors for applying from said source a unidirectional electromotive'force derived from both half waves of said source between two of said utilization conductors and an electromotive force derived from the half waves of one direction, of said source, between one of said two and the third ofsaid utilization conductors, and providing a path independent of said source from said one of said two to said third of said utilization conductors. v v

3. A signaling system utilizing a circuit including the inductive windings of electromagnets suited for energization only by unidirectional current flow, signal initiating stations serially included in such circuit and involving facilities for establishing ground connections thereat, a grounded alternating current supply source and rectifying means connecting said source with said circuit so as to supply substantially unidirectional current thereto and to provide paths which exclude .said source for conduction of circulating current through said circuit and between respective sides of said circuit and the ground.

4. In a signal system, an alternating current source, a conductor and a signaling current loop including signal manifesting devices therein adjacent to the ends thereof and signal initiating stations each comprising means for governing the effectiveness of, a-connection between said conductor and said loop, and rectifying means having input and output terminals, said input terminals being connected to said source and said output terminals and one of said input terminals being connected to the ends of said loop and to said conductor, respectively.

5. In a signal system, an alternating current source, a conductor and a signaling current loop including signal initiating stations each comprising means for formulating a code signal and ends of said loop and said output terminals, a

conductor through which emergency connection may be established with said loop through one or more of said stations, and a manifesting device connected between said conductor and one of the input terminals of said rectifying means.

7. In a signal system, a pair of alternating current supply conductors, a signaling loop having provisions whereby it may be connected to ground and including signaling devices responsive to unidirectional current fiow, and four asymmetrically conducting rectifyingunits, one of which units is connected for conducting current from one end of said loop to one of said supply conductors, another unitfrom said end of said loop to the ground and to the other of said supply conductors, and the remaining two units from the respective supply conductors to the other end of said loop.

8. Current supply equipment for applying energy from a two-conductor alternating current source to a three-conductor utilization system, comprising three asymmetrically conducting rectifying units, one of which units is connected for conducting current from one of said utilization conductors to one of said source conductors, another unit from said one to another. of said utilization conductors, andthe remaining unit from one of the source conductors to the third utilization conductor, a connection between the second named utilization conductor and the second source conductor, and means for formulating signaling impulses through paths resultant from serialconnections between different pairs of said system conductors.

9. Means for operatively associating a twoconductor source of alternating current with a three-conductor utilization system comprising a current path between a utilization system conductor and an alternating current source conductor, current paths between the other two utilization system conductors and the other source conductor and between one of said two utilization conductors and said first named source conductor, asymmetric valve equipment included in said first and last named paths and in one only of said second named paths to facilitate unidirectional current flow through a path including' said source, said first named path and said one of said last named paths as well as through paths excluding said source and extending between said one of said last named utilization conductors and respective ones of the other utilization conductors, and means for formulating signaling impulses through paths resultant from serial connections between different pairs of said system conductors.

10. A signal system comprising an alternating current source, a signaling current path having two terminals, a conductor and provisions whereby it may be connected to a point of said path, and means connected to said terminals supplying thereto substantially unidirectional current flow from said source and urging alternate current fiow, derived from the entire electromotive force of succeeding half-waves of said source, between said conductor and the respective terminals of said path.

11. A signal system comprising an alternating current source, a signaling current path having two terminals and signal initiating means and signal manifesting means therebetween, a conductor including signal manifesting means through which an emergency connection may be established between said source and said path, and means connected to said terminals for supplying thereto substantially unidirectional current flow from said source and urging alternate current flow, derived from the entire electromotive force of succeeding half-waves of said source,through circuits formed by said conductor and the portions of said path on respective sides of an emergency connection. v

12. A'signal system comprising an alternating current source, a normally closed circuit having signal initiating means and signal manifesting means in series therein, a conductor through which an emergency connection may be established between said source and any point of said circuit, and means for applying unidirectional current impulses from "said source to said manifesting means through said conductor and an associated part of said circuit, and for supplying a substantially continuous unidirectional current to said manifesting means through said circuit independently of said conductor.

13. A signal system comprising an alternating current source, a signaling current path hav-- ing two terminals, a signaling current conductor having provisions whereby it may be connected with said path, and means for continuously supplying a substantially unidirectional electromative force, derived from succeeding half-waves of said source, to said terminals and for applying the entire electromotive force of alternate halfwaves of said source between said conductor and respective terminals of said path, the resultant direction of the electromotive force applied to various portions of said path being unaffected by the establishment of said emergency connection.

14. Means for operatively associating a source of single phase alternating current with a threeconductor utilization system comprising connections between the first and second system conductors and one terminal of said source and connections between said second and the third sys tem conductors and the other terminal of said source, and asymmetric conductors in each of said connections between said second named conductor and the respective terminals of said source, means for formulating signaling impulses through paths resultant from serial connections between different pairs of said system conductors, one of said asymmetric conductors providing a unidirectional current path between said second and third system conductors and between one of said last named system conductors and said second named terminal.

15. Means for operatively associating a source of single phase alternating currentwith a threeconductor utilization system, comprising a connection between one system conductor and one terminal of said source and connections between the other system conductors and the other terminal of said source, an asymmetric conductor in said first named connection, an asymmetric conductor in one of said second named connections, and an asymmetric conductor between said first named terminal and the system conductor associated with said one of said second named connections, means for formulating signaling impulses through paths resultant from serial connections between different pairs of said system conductors, said asymmetric conductors providing a unidirectional current path from said source through said first connection and one of said other connections, and between said first system conductor and said system conductor associated with said one of said second named connections.

16. A signal system comprising a source of alternating current, a signaling loop having terminals, a conductor through which emergency connections may be selectively established with various portions of said loop, current detecting means in said conductor operative with unidirectional current, rectifying means associated with said conductor for supplying said detecting means with unidirectional current, and rectifying means associated with said source for supplying said terminals of said loop with unidirectional current and supplying alternating current between said conductor. and either one of said terminals.

17. In a signal system, a signaling loop having provisions whereby it may be connected to ground, an alternating current source, and full wave rectifying means having two input terminals connected to said source and two output terminals, said output terminals being connected to the respective ends of said loop for supplying substantially unidirectional current thereto and one of said input terminals being connected to ground.

18. In central oilice equipment for use in a signaling system of the type having a signaling current path and a ground or common return conductor at times connected to said path, comprising terminals for the respective ends of said path and a third terminal for said conductor, an alternating current source, connections between said source and respective ones of said terminals, the connections to two of said terminals respectively including unidirectional conducting means and being so applied to said source as to urge current flow of one series of half waves between such two terminals passing in a certain direction through a predetermined one of said connections, and the remaining connection including unidirectional conducting means and being so applied 20 to said source as to urge current fiow of the other series of half waves between such connection and said predetermined one of the first named two connections, said current flow passing through said predetermined one of said connections in the 25 opposite direction, and signal manifesting means responsive to current flow in respective ones of said first named two connections.

19. Central ofiice equipment for use in signaling systems of the type where a signaling current 3 path and a ground or common return conductor may at times be connected, comprising terminals for the respective ends of said path and a third terminal for said conductor, a source of alternating current, connections between the first and 35 second path terminals and one terminal of said source and connections between said second and the ground terminal and the other source terminal, asymmetric conductors in each of said connections between said second named terminal 40 and the respective source terminals, one of said asymmetric conductors providing a unidirectional current path between said second path terminal and said ground terminal, and between one of whereby establishment of a connection between 55 said first named terminals will cause full wave rectified current flow through both of said responsive devices and establishment of a connection between one of said first named terminals and said third named terminal will cause halfwave unidirectional current flow through one of said devices and establishment of a connection betweeen the other of said first named terminals and saidthird terminal will cause half-wave unidirectional current fiow through the other of said devices. I

21. Central ofiice equipment for a direct current emergency signaling system comprising rectifying means for applying energy from a two conductor alternating current source to three terminals of a direct current circuit, and electroresponsive devices serially connected between direct current output terminals of said rectifying means and respective ones of two of said terminals, said rectifying means comprising asymmetric conductors connected between said source and said devices whereby establishment of a connection between said first named terminals will cause full wave-rectified current flow through both of said responsive devices and establishment of a connection between one of said first named terminals and said third named terminal will cause halfwave unidirectional current flow through one of said devices and establishment or a connection between the other oi said first named terminals and said third terminal will cause half-wave unidirectional current flow through the other of said devices.

22. In a signaling system utilizing a source of alternating electromotive force and comprising three conductors which may at times be connected in any combination of two or three, means for applying consecutive one-halt cycles of substantially full alternating electromotive force from said source between one of said conductors and the other two conductors, alternately, and said iull alternating electromotive force between said other two conductors.

23. A current supply equipment comprising full wave rectifying means for applying energy from a two conductor alternating current source to a three conductor utilization system which utilization conductors may at times be interconnected in any combination of two or three, said rectifying means being connected between the source conductors and two of said utilization conductors and the third utilization conductor being connected to one of said twosource conductors.

24. In a signal system, an alternating current source, rectifying means having input terminals connected to said source and output terminals, a plurality of signal initiating stations, .a circuit connected to said output terminals including said 15 of said rectifying means and said circuit through one or more or said signal initiating stations.

CLARENCE E. BEACH. 

